New explosive



United States Patent Ofifice 2,992,087 Fatented July 11, 1961 2,992,087 NEW EXPLOSIVE Hartwell H. Fassnacht, Oak Valley, Robert W. Felch,

Wenonah, and Charles D. Forrest, Westville, N..l., assignors to I. du Pont de Nemours and Company, Wilmington, Deh, a corporation of Delaware No Drawing. Filed Nov. '3, 1959, Ser. No. 850,546 '7 Claims. (Cl. 52-13) The present invention relates to an explosive composition. More particularly, the present invention relates to a flexible self-supporting explosive composition containing pentaerythritol tetranitrate of specific particle size and to a method of fabricating the composition. This application is a continuation-in-part of our application, Serial -No. 763,182, filed September 25, 1958, now abandoned,

high explosive in a rigid annular container made of paper or the like. These containers must be slipped over the metallic element and a metal sleeve and, thus, are subjected to considerable stress which, in many cases, causes rupture of the necessarily rigid but light weight container. Moreover, because of their rigidity, many of these explosive units are broken during storage and transport. Obviously, elimination of this container and provision of a tough self-supporting unit would be very advantageous. Moreover, the desirability of using tough sheets of explosive which are cohesive enough to be cut, molded, or otherwise deformed to metal as in the method of workhardening described in detail in US. Patent 2,703,297

(N. A. MacLeod, March 1, 1955) is expressed in this patent. In shaped-charge perforators, the substitution of cohesive, self-supporting contoured shapes of explosive for the presently used charges of explosive which are pressed into a casing would facilitate the preparation of such perforators. Further, an explosive composition capable of being extruded into cords represents a long-felt need. Such extruded cords are suitable for use in the mining and quarrying industries as fuses or initiators in the manner of the well-known Primacord and additionally in various special applications, such as release devices, alarm systems, and the like.

Various factors and requirements are involved in the fabrication of a satisfactory self-supporting explosive composition. Naturally, the composition must have acceptable explosive properties. Namely, it must be capable of propagating reliably the detonation at high velocity, i.e., at a rate of the order of 5000 or more meters per second, even when the explosive loading is low. Secondly, it must have adequate sensitivity with respect to initiation, that is, the composition must be initiable by the customary initiation means, for example the standard blasting caps, preferably by those caps having low-weight base charges and thus producing weak initiation stimuli. This property of an explosive composition conventionally is termed its cap sensitiveness. In contrast to the high cap-sensitiveness desired in an explosive composition, its impact sensitiveness desirably is low. Impact sensitiveness, which indicates the sensitivity of the explosive to mechanical shocks, usually is determined by trial and error in the drop test, in which a weight, usually of S-kilograms, is dropped upon the explosive from various heights. Drop test results are reported in inches, which correspond to the distance which the Weight must fall to effect initiation. Obviously, those compositions which are initiated by the weight falling short distances, e.g., about 10 inches or less, are of high impact sensitiveness, whereas those initiated only when the weight falls considerable distances, e.g., 40 to 56 inches, are of low impact sensitiveness. In some cases detonation cannot be effected even when the weight falls the maximum distance, i.e., 56 inches, and in these cases the explosive generally is termed impact insensitive. At times, the drop test is modified to render it more severe by applying grit to the explosive. The presence of grit causes greater sensitiveness because of increased friction. Thus, this modified drop test reflects not only the impact but also the friction sensitiveness of the composition.

In addition to the explosive properties prerequisites, some of which were afore-described, the self-supporting explosive composition must possess certain characteristics with respect to physical form. Its nature must be such that it can be readily formed into the necessary configurations, for example sheets, cords, tapes, or contoured bodies of essentially uniform density. These configurations must retain the desired form under conditions of handling, transport, and storage. That is, the configurationsmust not lose their dimensional stability, i.e., they must not stretch or shrink, under these conditions, inasmuch as such changes in dimension would result in undesirable variations in weight of explosive per unit of area in the configuration, nor should the configurations be so soft or friable, i.e., clay-like, that their dimensions, i.e., thickness, length, or width, are easily altered during handling to preclude uniformity of explosive per unit of area. The units formed from the composition should be tough, i.e., strong or firm in texture but flexible and not brittle, to provide the proper adaptability to a given application. The composition must also be water-resistant, inasmuch as the operations complicating the storage, handling, and use of compositions and units which are not water-resistant make such compositions valueless.

Lastly, but not least importantly, the explosive composion must be easily and safely fabricated, as a complex and hazardous manufacturing operation obviates to an appreciable extent any advantageous features of explosive or physical properties of a given self-supporting explosive composition.

Accordingly, an object of the present invention is the provision of a self-supporting explosive composition which is easily and safely manufactured and readily formed into any desired configuration. Another object of the present invention is the provision of a water-resistant self-supporting explosive composition which retains its initial plasticity and explosive characteristics after prolonged exposure to adverse conditions. A still further object is the provision of a self-supporting composition in the form of sheets, cords, tapes, contoured shapes and the like, which configurations possess desirable physical properties. An additional object is to provide a flexible explosive composition which contains an improved additive which imparts higlrly desirable features thereto. Other objects will become apparent as the invention is further described.

We have found that the foregoing objects are achieved when we provide an explosive composition comprising at least 44% by weight of PETN of particles having a maximum dimension in the range of 0.1 to 10 microns, the average maximum dimension being in the range of 0.1 to 2 microns, 6.5 to 14% by weight of soluble nitrocellulose having a degree of polymerization of 2000 to 3000, and 15 to 35% by weight of a trialkyl ester of 2- acetoxy-1,2,3-propanetricarboxylic acid wherein each alkyl group contains from 2 to 8 carbon atoms. Tributyl 2-acetoxy-1,2,3-propanetricarboxylate represents a preferred specie. This compound has a molecular weight of 402.5, a flash point of 204 C., and a liquid range of 3 75 F. to about 285 F. Although we do not propose to limit ourselves by theoretical considerations, it is believed that the acetoxy group of the molecule contributes in some manner to the stability of the composition, particularly on prolonged storage.

Numerous attempts have been made in the past to discover an additive for nitrocellulose which would allow the fabrication of a plastic-type explosive having satisfactory sensitivity, safety properties, flexibility, water and weather resistance, and other properties ideally desirable for a plastic explosive composition. Undoubtedly, the most often employed additive for nitrocellulose has been nitroglycerin, which when added to nitrocellulose results in a jelly-like mass known in the art as blasting gelatin. The high sensitivity of such compositions, as well as the headache producing property imparted by the nitroglycerin, or other liquid nitric esters used a freezing point depressants constitute serious disadvantages of blasting gelatin. Consequently workers in the art have turned to the replacement of the nitroglycerin, which in blasting gelatin functions as the primary explosive, by less hazardous, often crystalline, high explosives or combinations of oxidizing agents and a fuel therefor, e.g., ammonium nitrate and a carbonaceous fuel, tetryl, or PETN. Hence, when the nitroglycerin is eliminated, it becomes necessary to substitute other materials in order to achieve the desired properties. Heretofore, the need for an entirely satisfactory additive for nitrocellulose-based plastic explosives has never been satisfied. Among the hundreds of materials which have been employed for this purpose are ineluded camphor, dibutyl phthalate, dioctyl phthalate, tributyl phosphate, aromatic nitro compounds, i.e., nitrobenzenes and toluenes, as well as countless others. Naturally, these various agents have met with varying degrees of success; however none has been entirely satisfactory for the fabrication of an easily formable, yet selfsupporting explosive composition. Some of these materials are incompatible with the other ingredients of the explosive composition, and after a short time may bleed, volatilize, or otherwise separate out leaving only a hard, brittle mass of explosive. Other agents, while apparently compatible with the explosive materials, after prolonged storage or exposure to severe weather conditions may become degraded to such an extent that the composition is rendered completely insensitive. Thus, the selection of an additive for explosive compositions having a nitrocellulose binder which is non-headache producing, completely compatible with the other explosive components, and stable on prolonged storage under extreme conditions represents an essential aspect of this invention in addition to the highly advantageous properties of the self-supporting plastic composition made possible thereby.

In accordance with the present invention, water-wet PETN of the specified particle size is mixed with the specified tricarboxylic acid ester. This mixing may be accomplished at room temperature for some examples given, but it is preferred that the mixing temperature be in the range of l30l35 F. The resultant mixture is blended for a few minutes, water, which is incompatible with the mixture, being displaced from the mixture and thereafter decanted from the mass. After removal of the water, the nitrocellulose which is wet with alcohol or water is added and mixed in until good incorporation is achieved, the mixture preferably being maintained at the elevated temperature.

The following examples serve to illustrate specific embodiments and advantageous features of the explosive composition of the present invention. However, they will be understood to be illustrative only and not as limiting the invention in any manner. Parts given in the examples are parts by weight unless otherwise specified. In all exemplified mixes, the PETN particles had a maximum dimension within the range of 0.1 to microns, the average thereof being 0.1 to 2 microns, and the nitrocellulose was a standard dynamite grade material of the soluble type having a nitrogen content of 12.3:0.3%

and a degree of polymerization of about 3000. All the drop test results reported in the examples were obtained by using a modification of the drop-test apparatus described in Bureau of Mines Bulletin 346 [Munroe and Tiffany, p. 72 (1931)]. In the modified apparatus a S-kg. weight is used, the maximum height from which the weight falls being 56 inches. The sample is placed in a small brass cup rather than directly on the anvil.

Example 1 Water-wet PETN in the amount of 113 parts (dry basis) was introduced into a mixer and brought to a temperature of about -135 P. Then 70 parts of tributyl 2-acetoxy-1,2,3-propanetricarboxylate was added to the heated PETN. The resultant mixture was mixed for about two minutes, the elevated temperature being maintained, and the water separating rapidly from the mixture. At the end of this time, the water was decanted, leaving an essentially uniform blend of the crystalline PETN and the tricarboxylate. Then, alcohol-wet nitrocellulose in the amount of 17 parts (dry basis) was added to the mixer, and mixing was continued at the elevated temperature for an additional 10-15 minutes until a uniform blend was ob tained, the alcohol evaporating rapidly during the mixing. Thereafter, the formulation was removed from the mixer.

The resultant composition while hot resembled soft clay and upon cooling became somewhat tougher and more like rubber. A portion of the material was passed through aluminum rollers until a sheet of uniform thickness was obtained. In appearance, the sheet resembled an oversized stick of chewing gum and was about 40 mils thick. The sheet detonated at a velocity of 6400 meters per second when initiated by a blasting cap having a base charge of 1.5 grains of PETN.

The sheet had a uniform density of 1.5 grams per cubic centimeter and failed to be initiated in the before-mew tioned drop test by the drop of a 5 kg. weight from a height of 56 inches. In physical characteristics, the sheet was tough, and essentially nonresilient. Normal handling of the sheet resulted in no alterations in its dimensions. Its dimensional stability (absence of stretching or shrinking) and flexibility were very good after storage at 10 and +160 F. for several months. The appearance and cap-sensitiveness of the sheet were not altered by extended, i.e., 6 months, storage under water.

Example 2 A composition containing 72% PETN of the specified particle size, 6.5% nitrocellulose and 21.5% of tri(2- ethylhexyl) Z-acetoxy-l,2,3-propanetricarboxylate was prepared according to the method described in Example l.

The composition at room temperature was readily moldable and was easily rolled into self-supporting sheets. Sheets of the material stored at 10 F., at room temperature, and at F. for 6 weeks displayed no loss in flexibility or in case of initiation. When initiated by a 1.5 grain PETN cap, they detonated at a velocity of 6900 meters per second. Sheets prepared, however, from a similar composition containing only 5 %nitrocellulose and 73.5% PETN and 21.5% of the tri(2-ethylhexyl) ester were easily deformed by handling, had little strength, and were not self-supporting.

Example 3 The procedure of Example 1 was repeated with the exception that 30 parts of the tributyl 2-acetoxy-1,2,3-propanetricarboxylate was used and 34 parts of dinitrotoluene was added to the PETN prior to addition of the tricarboxylate. Sheets formed from the resultant composition had a density of 1.55 gram per cubic centimeter and detonated at a velocity of 6700 meters per second. Sheets of this composition were equivalent to those of the Example 1 formulation in cap and impact sensitiveness, detonation propagation, and in appearance.

Example 4 In accordance with the procedure of Example 3, a formulation was prepared containing 60% PETN, 8.5% nitrocellulose, 24% tributyl Z-acetoxy-1,2,3-propanetricarboxylate, and 7.5% of an equiweight mixture of dinitrotoluene and trinitrotoluene. Sheets prepared from this formulation were initiated by a 1.5-grain PETNblasting cap and detonated at a velocity of 6700 meters per second. The flexibility of the sheet at 10 F., room temperature, and +120 F. was excellent, and a sheet of 30 mils thickness and having an explosive loading of only about 0.7 gram per square inch detonated consistently, at a uniform rate when initiatedby a standard No. 6 blasting cap.

Example 5.

A quantity of the composition prepared in Example 1 Was placed in a conventional ram-type extruder of 4- pound capacity. The composition was maintained at a temperature of about 130 F. during extrusion. Flexible uniform cords inch in diameter were obtained. These cords having an explosive loading of about 20 grains per foot were detonated reliably by a standard No. 8 seismograph cap, even when exposed to hydrostatic pressures of 10,000 pounds per square inch. The detonation velocity of the cords was over 6400 meters per second.

Example 6 The die of the extrusion apparatus of Example was modified in order to extrude the cords in A inch diameter and with a continuous V-shapednotch in their surface. The cords thus obtained were identicalto the sheet of Example 1 in explosive characteristics. By taking advantage of the Munroe effect, the V-shaped cords were used to sever or cut thin sheet metal and similar materials. Similarly, explosive cords in the form of seamless hollow tubing were prepared.

The following examples are intended for a comparison between the properties of the plastic composition prepared according to our invention and those of compositions prepared by using conventional nitrocellulose additives.

Example 7 To 76.63 grams of PETN heated to 130 F. was added a molten blend containing 16.64 grams of dinitrotoluene and 5.55 grams of trinitrotoluene. Nitrocellulose in the amount of 1.18 grams was added to the heated mixture and m'uring was continued for 20 minutes. The warm composition when removed from the mixer was weakly cohesive and somewhat moldable. At room temperature, however, the composition set up to a hard composition resembling chalk or baked clay.

Example 8 A composition similar to that of Example 7 was prepared except that 15 parts of dibutyl phthalate was used in place of the blend of aromatic nitro compounds. The resulting composition, while initially moldable and flexible at room temperature, became brittle and friable after storage at 140 F. for a period of six weeks.

As shown by the foregoing examples, a water-resistant self-supporting explosive composition, which is readily transformed into shaped units, for examples, sheets, cords, or tubes, which are tough and essentially nonresilient, can be easily prepared in accordance with the present invention. The composition, in addition to having its requisite physical properties, has excellent explosive properties. That is, it is readily initiated by blasting caps of low strength, it is of low impact sensitiveness, and it propagates the detonation reliably. No alternations in either physical properties or cap-sensitiveness of the units of this composition are brought about by prolonged exposure to water.

We have found that in order to obtain sheets of the necessary physical properties, at least 6.5% of nitrocellulose must be incorporated into the formulation.

Lesser quantities of nitrocellulose, as illustrated by Example 2, give a cohesive but soft clay-like mixture forming sheets which are not tough but are flimsy and claylike in consistency, and thus essentially useless for the afore-described explosive applications. Inasmuch as the explosive properties of the composition, i.e., its cap sensitiveness and capacity to detonate reliably, are deleteriously affected by the inclusion of more than about 14% of the nitrocellulose, the incorporation of more than 14% nitrocellulose in the formulation is undesirable. Furthermore, more than 14% nitrocellulose can be incorporated only with great difliculty if at all. However, since the use of 65-14% of the nitrocellulose gives a composition of very satisfactory physical properties, the upper limitation on nitrocellulose content imposed by the requirements of explosive activity and ease of mixing constitutes no drawback.

We have found that the PETN used in the composition must be of special, highly sensitive type, to compensate for the desensitization effected by inclusion of sufficient nitrocellulose to provide the desired physical properties. That is, the PETN particles must be of such size that their maximum dimension is within the range of 0.1 to 10 microns, the average maximum particle dimension being within the range of 0.1 and 2 microns. When other grades of PETN, for example that standard granulation termed in the art cap-grade PETN, are substituted for the afore-specified material, the cap sensitiveness of the composition is decreased to such an extent that the composition is of no value. The PETN must be incorporated in the amount of at least 44% to insure adequate sensitivity, the upper limit in general being set by the limitations on the proportions of the other components.

The function of the nitrocellulose constitutent of the composition is to provide in it the desired physical properties and form, its contribution to the explosive properties of the sheet being secondary. Therefore, the requirements of the nitrocellulose are based upon its activity as a binding agent rather than as an explosive. For this reason, the criticality with respect to the type of nitrocellulose used resides in its solubility characteristics and viscosity rather than in its nitrogen content. Suitable nitrocellulose is of the soluble type, the term conventionally used in the art to differentiate between those nitrocelluloses having a nitrogen content of about 7% up to about 13% and relatively soluble in an alcohol-ether medium and those nitrocelluloses, generally termed-guncottons, having a nitrogen content of 13% and greater and insoluble in the alcohol-ether medium. Throughout the specification and claims, the term soluble nitrocellulose is used in accordance with the previously described conventional meaning of the term.

Moreover, the nitrocellulose must be of the highviscosity type. Because of the interrelationship between viscosity and degree of polymerization, i.e., the average number of anhydroglucose units in the chain, or molecule, and because of the ease of definition inherent to the use of the term degree of polymerization rather than intrinsic viscosity, we choose to express the viscosity of the nitrocelluloses in terms of its degree of polymerizations. Those nitrocelluloses which may be employed in the present formulation have an average degree of polymerization within the range of 2000 and 3000. In other words, the molecules of the nitrocellulose used contain on an average 2000-3000 anhydroglucose units. The high viscosity nitrocellulose may be obtained by using one grade ofnitrocellulose having a degree of polymerization of 2000-3000 or by blending several grades of nitrocellulose of varying degrees of polymerization in such proportions to achieve an average degree of polymerization within the specified range. As stated before, the nitrogen content of' the nitrocellulose, except as solubility is related to nitrogen content, is not a critical feature of the presentinvention. Obviously, those nitrocelluloses having a nitrogen content of 13% or more are of the insoluble type and thus are outside the scope of the present invention. However, any nitrocellulose of the soluble type, whether it be the socalled industrial nitrocellulose or the so-called pyrocotton, or explosive material, and having the necessary high intrinsic viscosity gives satisfactory formulations and, thus, is within the scope of the present invention. Because of its ready availabilty and high intrinsic viscosity, dynamite-grade nitrocellulose having a nitrogen content of 12.0 to 12.6% is preferred.

Although we have found tributyl 2-acetoxy-1,2,3-propanetricarboxylate to be the preferred additive, other trialkyl esters of 2-acetoxy-1,2,3-propanetricarboxylic acid wherein each alkyl group contains 2 to 8 carbons are suitable. For example, the triethyl, tripropyl, tripentyl, trihexyl, triheptyl esters and their isomers, as well as the exemplified tri(2-ethylhexyl) esters, will provide an entirely satisfactory composition. The higher alkyl esters do not function satisfactorily owing to their reduced activity toward the nitrocellulose which makes them incapable of producing explosive compositions having the required physical properties.

If desired, an aromatic nitro compound or mixtures thereof may be added to the mix in order to impart increased fiuidity and thus aid in ingredient incorporation. Naturally, these components will be added in the liquid state. It is to be understood, however, that the addition of the aromatic nitro compound merely represents a manufacturing expedient, its presence being in no manner critical to the composition.

As has already been stated, the mixing procedure preferably is effected at elevated temperature, i.e., at a temperature above 100 F. The PETN preferably is used in water-wet state to decrease safety hazards. It and the 2-acetoxy-1,2,3-propane tricarboxylic acid ester are mixed together until a uniform blend is obtained, the water added with the PETN separating during the mixing and thereafter being removed, e.g. by decantation or suction. Then, nitrocellulose, which is wet with a solvent such as alcohol or water in accordance with conventional safety precautions, is added to the PETN blend at the elevated temperature and mixing is continued at such temperature until a uniform blend is apparent, the solvent evaporating ofi in major part during the mixing, slight quantities of residual alcohol or Water not being deleterious to the sheet. Because the addition of water and alcohol to the system thus constitutes no drawback, the composition may be prepared in a very safe manner. The formulation then is removed from the mixer and can be readily formed into the desired configurations. As has been exemplified, the composition may be passed through rollers to give sheets or tapes of the desired thickness. With certain formulations, the use of heated rollers is desirable to facilitate the rolling operation. Of course, the composition may be formed into other configurations such as contoured bodies by operations such as molding and by extruding into tubes or cords, as exemplified. Moreover, sheets may also be prepared by methods other than rolling, i.e., by slicing, cutting, or extruding the mass.

The density of the composition of the present invention generally is high, i.e. about 1.5 grams per cubic centimeter. The explosive loading of the sheet, that is the weight of composition per unit area, is controlled by the thickness of the sheet. For certain applications, a sheet having a relatively low explosive loading may be desired and, thus, thin sheets will be prepared. On the other hand, for some appications heavy loadings are preferable and thick sheets will be used. As illustrated, the minimum thickness of sheet required to support the detonnation will vary as the exact proportions of components within the specified ranges vary, as will the density, cap sensitivity, and detonation velocity to some extent. Thereby, a certain versatility in the properties of the sheet is possible by proper selection of ingredient pro 8 portions, permitting its use in -a variety of applications of explosives. V

The present invention has been described in detail in the foregoing. However, it will be apparent to those skilled in the art that many variations are possible without departure from the scope of the invention. Therefore, we intend to be limited only by the following claims.

We claim:

1. A self-supporting explosive composition of high cap-sensitiveness and low impact-sensitiveness consisting essentially of at least 44% by weight of pentaerythritol tetranitrate having a maximum particle dimension within the range of 0.1 and 10 microns, the average maximum particle dimension being within the range of 0.1 and 2 microns, 65-14% by Weight of soluble nitrocellulose having an average degree of polymerization within the range of 2000 and 3000, and 15-35% by weight of a trialkyl ester of 2-acetoxy-1,2,3-propanetricarboxylic acid wherein each alkyl group contains 2 to 8 carbon atoms.

2. An explosive composition according to claim 1, wherein said ester of 2-acetoxy-1,2,3-propanetricarboxylic acid is the tributyl ester.

3. A self-supporting explosive composition in sheet form of high cap-sensitiveness and low impact-sensitiveness consisting essentially of at least 44% by weight of pentaerythritol tetranitrate having a maximum particle dimension within the range of 0.1 and 10 microns, the average maximum dimension being within the range of 0.1 and 2 microns, 65-14% by Weight of soluble nitrocellulose having an average degree of polymerization within the range of 2000 and 3000, and 15-35% by weight of a trialkyl ester of 2-acetoxy-1,2,3-propanetricarboxylic acid wherein each alkyl group contains 2 to 8 carbon atoms.

4. An explosive composition in the form of extruded cords of high cap-sensitiveness and low impact-sensitiveness consisting essentially of at least 44% by weight of pentaerythritol tetranitrate having a maximum particle dimension within the range of 0.1 and 10 microns, the average maximum dimension being within the range of 0.1 and 2 microns, 65-14% by weight of soluble nitrocellulose having an average degree of polymerization within the range of 2000 and 3000, and 15-35% by weight of a trialkyl ester of 2-acetoxy-1,2,3-propanetricarboxylic acid wherein each alkyl group contains 2 to 8 carbon atoms.

5. An explosive composition according to claim 4, wherein said extruded cords contain a V-shaped indentation.

6. A method for the preparation of a self-supporting explosive composition of high cap-sensitivity and low impact-sensitivity which comprises mixing at least 44% by weight on dry basis of water-wet pentaerythritol tetranitrate having a maximum particle dimension within the range of 0.1 and 10 microns, the average maximum particle dimension being within the range of 0.1 and 2 microns, with 15-35% by weight of a trialkyl ester of 2- acetoxy-l,2,3-propanetricarboxylic acid wherein each alkyl group contains 2 to 8 carbon atoms, adding 65-14% by weight on dry basis of solvent-wet soluble nitrocellulose having an average degree of polymerization within the range of 2000 and 3000, admixing said nitrocellulose with the blend of said pentaerythritol tetranitrate and said trialkyl ester, and thereafter rolling the mixture into sheets.

'7. A method according to claim 6, wherein said pentaerythritol tetranitrate and said trialkyl ester are admixed in the presence of up to 25% by weight of at least one aromatic nitro compound selected from the group consisting of dinitrotoluene and trinitrotoluene.

References Cited in the file of this patent FOREIGN PATENTS 481,223 Canada Feb. 19, 1952 

1. A SELF-SUPPORTING EXPLOSIVE COMPOSITION OF HIGH CAP-SENSITIVENESS AND LOW IMPACT-SENSITIVENESS CONSISTING ESSENTIALLY OF AT LEAST 44% BY WEIGHT OF PENTAERYTHRITOL TETRANITRATE HAVING A MAXIMUM PARTICLE DIMENSION WITHIN THE RANGE OF 0.1 AND 10 MICRONS, THE AVERAGE MAXIMUM PARTICLE DIMENSION BEING WITHIN THE RANGE OF 0.1 AND 2 MICRONS, 6.5-14% BY WEIGHT OF SOLUBLE NITROCELLULOSE HAVING AN AVERAGE DEGREE OF POLYMERIZATION WITHIN THE RANGE OF 2000 AND 3000, AND 15-35% BY WEIGHT OF A TRIALKYL ESTER OF 2-ACETOXY-1,2,3-PROPANETRICARBOXYLIC ACID WHEREIN EACH ALKYL GROUP CONTAINS 2 TO 8 CARBON ATOMS. 